#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;

#define ll long long
#define INF (1 << 30)
#define INFLL (1LL << 60)

int main() {
	int n,m;
	int where[1001] = {};
	int migi[1001] = {},hida[1001] = {},s = 0;
	for(int i = 1;i < 1001;i++){
		migi[i] = INF / 2;
		hida[i] = INF / 2;
	}
	cin >> n >> m;
	for(int i = 0;i < m;i++){
		cin >> where[i];
	}
	sort(where,where + m);
	int now = 1,how = 0;
	for(int i = 0;i < m;i++){
		if(where[i] < 0) how++;
		if(where[i] == 0) s++;
	}
	for(int i = 0;i < m;i++){
		if(where[i] > 0){
			migi[now] = where[i];
			now++;
		}else{
			hida[how] = abs(where[i]);
			how--;
		}
	}

	int ans = INF;
	for(int i = 0;i <= n;i++){
		ans = min(ans,min(2*migi[i] + hida[n - s - i],2*hida[i] + migi[n - s - i]));
	}
	cout << ans << endl;
	return 0;
}